Over 80,000 craniofacial reconstructions are performed annually in the United States. Although allograft and autograft tissues are the most commonly utilized graft materials, they have a failure rate ranging from 13–30%. Synthetic materials that can be produced in large quantities have been developed in numerous forms as alternatives to the traditional bone derived graft materials. Ceramic materials such as hydroxyapatite (HA), bioglasses, and tricalcium phosphate, and polymeric materials including polyethylene and silicone are available commercially in a wide variety of craniomaxillofacial procedures. All commercially available systems have at least one of the following shortcomings; 1) poor adaptation to recipient sites, 2) insufficient biological fixation, and 3) inadequate mechanical properties. The ability to manufacture implants that can simultaneously address all three problems is both commercially and medically significant.
Implants which do not match the unique anatomical constraints of the defect sites often require manual modification (grinding) of the implants, and/or the recipient bone. Additional modification is often necessary on the external surfaces to produce the appropriate facial contours. Although manual alteration can be trivial in some cases, extensive modifications are often necessary. Pre-fabricated elastomeric silicone implants adapt easily to the recipient sites, but they are generally characterized by soft tissue encapsulation, bone resorption, migration, and distortion (drooping). The latter problems are believed to be related to the lack of biological fixation, or tissue penetration into the implant surface. Porous implants allow tissue penetration, but their porous nature severely degrade their mechanical properties. This is particularly true for porous ceramics implants, which tend to break during extensive manual modifications. Dense ceramic materials typically have greater load bearing ability than their porous counterparts, but their excessive stiffness (high modulus) may induce stress shielding.
In summary all commercially available systems have at least one of the following shortcomings; 1) poor adaptation to recipient sites, 2) insufficient biological fixation, and 3) inadequate mechanical properties. Implants which can simultaneously address all three problems can be both commercially and medically significant.